Oil lamp



FIG. 1 is a left front perspective view of an oil lamp embodying my new design;

FIG. 2 is a right side elevational view thereof, the left side being identical;

FIG. 3 is a rear view thereof;

FIG. 4 is a top view thereof; and

FIG. 5 is a bottom view thereof. 

The ornamental design for an oil lamp, as shown and described. 